In the prior art, the process of burying the plug made of tungsten in the contact hole, which is formed in an insulating film on the silicon substrate, contains the steps of forming a contact hole in the insulating film, cleaning the inside of the contact hole by the negative sputtering, forming a titanium film on an upper surface of the insulating film and an inner surface of the contact hole by the physical vapor deposition (PVD), growing a titanium nitride film on the Ti film by the metal organic chemical vapor deposition (MOCVD), burying a tungsten in the contact hole, and then removing the tungsten, the TiN film, and the Ti film on the insulating film by the chemical mechanical polishing (CMP). The tungsten buried in the contact hole serves as the plug.
Japanese Laid-open Patent Publication No. Hei-8-176823 discloses the process of forming the Ti film before growing the tungsten or the aluminum in the contact hole of 0.2 μm diameter, wherein the process consists of the steps of supplying a reaction gas, which contains titanium tetrachloride and hydrogen rich, to the growth atmosphere and thereby removing a native oxide on a silicon substrate and then forming the Ti film by reducing a flow rate of H2.
Japanese Laid-open Patent Publication No. Hei-8-213343 discloses the process of forming the Ti film before growing the tungsten or the aluminum in the contact hole of 0.2 μm diameter, wherein the process consists of the step of reducing an amount of chlorine in the Ti film by flowing TiCl4 in a H2 rich condition.
Also, Japanese Laid-open Patent Publication No. 2001-326227 discloses the process comprising the steps of forming a hole in an insulating film on some layer, forming a barrier layer on an inner surface of the hole and an upper surface of the insulating film, vapor-phase depositing a copper seed layer on the barrier layer, and forming a copper bulk layer on the copper seed layer by the plating to bury the hole. A specific resistance of copper is 1.7 μΩ·cm, and is lower than a specific resistance 5.0 μΩ·cm of tungsten. Thus, the copper is expected as the good material to lower the contact resistance.
The copper is also used the plug that connect the impurity diffusion region in the silicon substrate and the wiring formed over the region. The copper plug that is shaped into the contact of 160 nm diameter is set forth in S. Demuynck, et al. Impact of Cu contacts on front-end performance: a projection towards 22 nm node, International Interconnect Technology Conference 2006, p. 178.